Genetic Variants of Interleukin-10 Gene Promoter are Associated with Schizophrenia in Saudi Patients: A Case-Control Study

IL-10 (-1082 G/A) polymorphism in Bataknese with schizophrenia

Objectives

Three biallelic polymorphisms at the promoter region of the interleukin-10 (IL-10) gene have been associated with susceptibility to schizophrenia. The aim of this case-control study was to investigate the association between IL-10 (-1082) G/A gene polymorphisms and schizophrenia among Bataknese, a native tribe inhabiting the North Sumatera province in Indonesia.

Methods

A total of 194 unrelated participants (n = 97 for each case and control groups) participated in this study. Polymerase chain reaction restriction fragment length polymorphism molecular genotyping was conducted to assess the genotype and allele distribution of IL-10 (-1082 G/A).

Results

Allele variations indicated that the dominant allele in the Batak tribe was allele A, whereas homozygous GG genotypes were not found in either group. The A allele and AA genotype were found to be risk factors for developing schizophrenia (OR = 2.26, 95% CI = 1.1825-4.3559 and OR = 2.56, 95% CI = 1.280-5.152, respectively).

Conclusion

Only the A allele and AA genotype of the IL-10 gene polymorphism at -1082 G/A contribute to schizophrenia susceptibility in Bataknese.

The association of cytokines genes (IL-6 and IL-10) with the susceptibility to schizophrenia: A systematic review and meta-analysis

Cytokines are among the important effectors and messenger molecules for restoring the homeostasis tissue after an inflammatory response. The association between IL-6 and IL-10 genes polymorphisms with the schizophrenia susceptibility have yielded controversial results. To reconcile the results, a systematic review followed by meta-analysis was performed to assess the association. We carried out literature searches of PubMed, Scopus, EBSCO, and Web of Sciences databases. Pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated to assess the strength of the association. Subgroup analysis, heterogeneity analyses, and publication bias were also calculated in the meta-analysis. A total of 22 case-control studies, consisting of 4,993 schizophrenic patients and 5,195 healthy controls, were included in the meta-analysis. The meta-analysis suggests that the IL-6 rs1800795 polymorphism displays a protective role against schizophrenia, while the IL-10 rs1800896 and rs1800872 polymorphisms confer an increased risk of schizophrenia. Similar results were found in subgroup analysis by ethnicity. We did not find association between IL-10 rs1800871 polymorphism and schizophrenia susceptibility. Finally, this meta-analysis suggested that the dysregulation of cytokines could lead to the pathogenesis of the schizophrenia.

Association of Single Nucleotide Polymorphisms of Cytokine Genes with Depression, Schizophrenia and Bipolar Disorder

Immune gene variants are known to be associated with the risk of psychiatric disorders, their clinical manifestations, and their response to therapy. This narrative review summarizes the current literature over the past decade on the association of polymorphic variants of cytokine genes with risk, severity, and response to treatment for severe mental disorders such as bipolar disorder, depression, and schizophrenia. A search of literature in databases was carried out using keywords related to depressive disorder, bipolar disorder, schizophrenia, inflammation, and cytokines. Gene lists were extracted from publications to identify common genes and pathways for these mental disorders. Associations between polymorphic variants of the IL1B, IL6, and TNFA genes were the most replicated and relevant in depression. Polymorphic variants of the IL1B, IL6, IL6R, IL10, IL17A, and TNFA genes have been associated with schizophrenia. Bipolar disorder has mainly been associated with polymorphic variants of the IL1B gene. Interestingly, the IL6R gene polymorphism (rs2228145) was associated with all three diseases. Some cytokine genes have also been associated with clinical presentation and response to pharmacotherapy. There is also evidence that some specific polymorphic variants may affect the expression of cytokine genes. Thus, the data from this review indicate a link between neuroinflammation and severe mental disorders.

A study of the association between polymorphisms in the genes for interleukins IL-6 and IL-10 and negative symptoms subdomains in schizophrenia

BACKGROUND

Schizophrenia is a severe mental illness manifested by various symptoms. Negative symptoms (NS) are associated with disability and poor function of patients. The study of NS neurobiology is complicated by their heterogeneity. Factor analysis revealed two distinct NS subdomains with different pathophysiological mechanisms: volitional pathology, including avolition and apathy (AA), and diminished expression (DE). Inflammation is one mechanism that may underlie NS, including their heterogeneity.

AIMS

To search for the association between genes for interleukins (IL-6 -174 G/C, IL-10 -592 C/A, and IL-10 -1082 G/A) and NS subdomains.

MATERIALS AND METHODS

The study included 275 patients with schizophrenia. NS factors were calculated based on the Positive and Negative Syndromes Scale.

RESULTS

There was a significant main effect of IL-10 polymorphisms on the AA, but not the DE subdomain. Mean score on the AA subdomain was higher in the IL-10 -592 AA compared to the CC genotype. Differences between IL-10 -1082 G/A genotypes were dose dependent. The lowest score was observed for the IL-10 -1082 GG genotype. The association between the IL-6 -174 G/C polymorphism and AA scores was close to the level of significance. Patients with the IL-6 -174 GG genotype had higher score compared to the AA genotype.

CONCLUSION

The results provide further neurobiological evidence for the validity of the NS factor categorization. An imbalance between pro-inflammatory and anti-inflammatory cytokines because of genetic variations is associated with the AA NS subdomain that is supposed to be a more severe aspect of psychopathology compared to the DE.

The Role of the IL-10 (-819C/T), TNFA (-308G/A) and ENOS (-786T/C) Polymorphisms of Impulsive and Aggressive Personality Traits in Cocaine/Crack Users

Cytokines and nitric oxide have been associated with impulsive and aggressive personality traits. We conducted the first study that investigated the role of SNPs in cytokines and nitric oxide genes and the influence in the progression of aggressive and impulsive behavior in 107 of cocaine and crack users. In this case-control, IL-10 (-819C/T), TNFA (-308G/A) and ENOS (-786T/C) polymorphisms were determined by Real-Time PCR. In addition, the relationship between these polymorphisms and Impulsivity and Aggression was determined. We found that the physical aggressiveness sub score was negatively correlated with the C allele of -819C/T polymorphism of the IL-10 (b = -0.14; p = 0.04). The T allele of the SNP -786T/C of the ENOS gene positively predicts traits of physical aggressiveness (b = 0.14; p = 0.04). The GA genotype (b = 0.22; p = 0.01) and the A allele (b = 0.15; p = 0.02) of -308 G/A polymorphism of the TNFA were positively correlated with aggressiveness physical. The GA genotype (b = 0.20; p = 0.03) was positively correlated with aggressiveness verbal. IL-10 (-819C/T), TNFA (-308G/A) and ENOS (-786T/C) polymorphisms might be associated with high risk of aggressive and impulsive behavior.

Genetic association study reveals impact of interleukin 10 polymorphisms on cognitive functions in schizophrenia

AIM

Cognitive deficits are the core factors impacting quality of life among patients diagnosed with schizophrenia. Effective method of treatment for this domain of symptoms remains lacking. Recent evidence suggests the link between impaired cognition and aberrant inflammatory response. Severity of symptoms might be linked to individual genetic predispositions and single-nucleotide polymorphisms (SNPs) in genes encoding interleukins and their receptors. Current genetic association studies include anti-inflammatory interleukins, such as IL10. Functional polymorphisms of IL10 (rs1800871, rs18008729) have been indicated to affect information processing in schizophrenia.

MATERIALS AND METHODS

In this study, we analyzed the potential impact of 27 functional SNPs in 8 cytokine genes on cognitive parameters measured by Wisconsin card-sorting test (WCST) in schizophrenia group (n = 150) and healthy controls (n = 152).

RESULTS

We found significant associations of two functional polymorphisms of IL10 (rs1800871, rs1800872) and WCST results. Allele A carriers in rs1800871 performed significantly better in Percent of Conceptual Level Responses (CLR%). Allele A carriers in rs1800871 and allele T carriers in rs1800872 obtained better results in Completed Categories (CC). The impact of illness duration was observed, with better performance of recent-onset patients.

CONCLUSIONS

Results of this study indicate that genetic variants of inflammatory response are associated with cognitive deficits in schizophrenia. The role of cytokines in schizophrenia need to be investigated in the aspect of pro-/anti-inflammatory imbalance. Altered inflammatory response promote chronic mild inflammation in the brain and aberrant synaptic plasticity.

C-Reactive Protein as a Peripheral Biomarker in Schizophrenia. An Updated Systematic Review

Objectives: The objective of this systematic review was to synthetize the published data on the relationships between elevated blood C-reactive protein (CRP) levels and schizophrenia (SZ) onset risk, illness characteristics and treatments, cognition and physical health. Method: The systematic bibliographic searches have been carried out according to the Cochrane methodology. Medline, web of science, Google Scholar with each database being searched from inception to November 2017. Results: 53 studies were included in the present review. While meta-analyses including case-control studies suggest a clear association between CRP and SZ, one other study has suggested that CRP-associated genes were associated with a lower risk of SZ onset. Increased CRP has been significantly associated with positive symptoms in acute phase psychosis, while studies including community-dwelling stabilized subjects did not find such an association. Abnormal CRP has been associated with a wide range of cognitive impairment in SZ stabilized individuals. Body Mass index has been extensively associated with increased CRP in SZ subjects; and increased CRP has been identified as a risk factor for metabolic syndrome and cardiovascular risk in SZ subjects. Increased CRP has also been associated with high nicotine dependence in SZ smokers and one study has suggested that increased CRP was associated with sedentary behavior. Conclusion: In the light of the above-mentioned studies, increased hs-CRP may be reasonably suggested as a marker for SZ onset risk, as well as a risk factor for increased positive symptoms, cognitive impairment, hypovitaminosis D, microbiota disturbances, cardiovascular and metabolic syndrome risk in SZ subjects, and increased nicotine dependence in SZ smokers. In case of increased CRP levels, anti-inflammatory strategies (add-on anti-inflammatory drugs including aspirin and omega 3 fatty acids, vitamin D supplementation, physical activity, probiotics) should be also further evaluated. Limits: Most of the studies were cross-sectional and cohort studies are needed to determine the temporal relationship between increased CRP and the psychiatric outcomes.

Family-based association study of interleukin 10 (IL10) and interleukin 10 receptor alpha (IL10RA) functional polymorphisms in schizophrenia in Polish population

Schizophrenia is a heterogeneous disorder and its etiology remains incompletely elucidated. Among possible causes, immunological factors have been implicated in its pathogenesis and course. Interleukin-10 (IL10) and it's receptor IL10RA may play an important role for immunological aspects in etiologies of major psychiatric disorders including schizophrenia. The aim of this study was to perform a transmission disequilibrium test (TDT) on a group of 146 schizophrenia trios from the Polish population. Functional polymorphisms from IL10 (rs1800872, rs1800871, rs1800896, rs1800890, and rs6676671) and IL10RA (rs3135932 and rs2229113) genes were analyzed. A lack of association with schizophrenia was detected for IL10 and IL10RA single polymorphisms and haplotypes.

Investigating the Causal Relationship of C-Reactive Protein with 32 Complex Somatic and Psychiatric Outcomes: A Large-Scale Cross-Consortium Mendelian Randomization Study

BACKGROUND

C-reactive protein (CRP) is associated with immune, cardiometabolic, and psychiatric traits and diseases. Yet it is inconclusive whether these associations are causal.

METHODS AND FINDINGS

We performed Mendelian randomization (MR) analyses using two genetic risk scores (GRSs) as instrumental variables (IVs). The first GRS consisted of four single nucleotide polymorphisms (SNPs) in the CRP gene (GRSCRP), and the second consisted of 18 SNPs that were significantly associated with CRP levels in the largest genome-wide association study (GWAS) to date (GRSGWAS). To optimize power, we used summary statistics from GWAS consortia and tested the association of these two GRSs with 32 complex somatic and psychiatric outcomes, with up to 123,865 participants per outcome from populations of European ancestry. We performed heterogeneity tests to disentangle the pleiotropic effect of IVs. A Bonferroni-corrected significance level of less than 0.0016 was considered statistically significant. An observed p-value equal to or less than 0.05 was considered nominally significant evidence for a potential causal association, yet to be confirmed. The strengths (F-statistics) of the IVs were 31.92-3,761.29 and 82.32-9,403.21 for GRSCRP and GRSGWAS, respectively. CRP GRSGWAS showed a statistically significant protective relationship of a 10% genetically elevated CRP level with the risk of schizophrenia (odds ratio [OR] 0.86 [95% CI 0.79-0.94]; p < 0.001). We validated this finding with individual-level genotype data from the schizophrenia GWAS (OR 0.96 [95% CI 0.94-0.98]; p < 1.72 × 10-6). Further, we found that a standardized CRP polygenic risk score (CRPPRS) at p-value thresholds of 1 × 10-4, 0.001, 0.01, 0.05, and 0.1 using individual-level data also showed a protective effect (OR < 1.00) against schizophrenia; the first CRPPRS (built of SNPs with p < 1 × 10-4) showed a statistically significant (p < 2.45 × 10-4) protective effect with an OR of 0.97 (95% CI 0.95-0.99). The CRP GRSGWAS showed that a 10% increase in genetically determined CRP level was significantly associated with coronary artery disease (OR 0.88 [95% CI 0.84-0.94]; p < 2.4 × 10-5) and was nominally associated with the risk of inflammatory bowel disease (OR 0.85 [95% CI 0.74-0.98]; p < 0.03), Crohn disease (OR 0.81 [95% CI 0.70-0.94]; p < 0.005), psoriatic arthritis (OR 1.36 [95% CI 1.00-1.84]; p < 0.049), knee osteoarthritis (OR 1.17 [95% CI 1.01-1.36]; p < 0.04), and bipolar disorder (OR 1.21 [95% CI 1.05-1.40]; p < 0.007) and with an increase of 0.72 (95% CI 0.11-1.34; p < 0.02) mm Hg in systolic blood pressure, 0.45 (95% CI 0.06-0.84; p < 0.02) mm Hg in diastolic blood pressure, 0.01 ml/min/1.73 m2 (95% CI 0.003-0.02; p < 0.005) in estimated glomerular filtration rate from serum creatinine, 0.01 g/dl (95% CI 0.0004-0.02; p < 0.04) in serum albumin level, and 0.03 g/dl (95% CI 0.008-0.05; p < 0.009) in serum protein level. However, after adjustment for heterogeneity, neither GRS showed a significant effect of CRP level (at p < 0.0016) on any of these outcomes, including coronary artery disease, nor on the other 20 complex outcomes studied. Our study has two potential limitations: the limited variance explained by our genetic instruments modeling CRP levels in blood and the unobserved bias introduced by the use of summary statistics in our MR analyses.

CONCLUSIONS

Genetically elevated CRP levels showed a significant potentially protective causal relationship with risk of schizophrenia. We observed nominal evidence at an observed p < 0.05 using either GRSCRP or GRSGWAS-with persistence after correction for heterogeneity-for a causal relationship of elevated CRP levels with psoriatic osteoarthritis, rheumatoid arthritis, knee osteoarthritis, systolic blood pressure, diastolic blood pressure, serum albumin, and bipolar disorder. These associations remain yet to be confirmed. We cannot verify any causal effect of CRP level on any of the other common somatic and neuropsychiatric outcomes investigated in the present study. This implies that interventions that lower CRP level are unlikely to result in decreased risk for the majority of common complex outcomes.

Association study of functional polymorphisms in interleukins and interleukin receptors genes: IL1A, IL1B, IL1RN, IL6, IL6R, IL10, IL10RA and TGFB1 in schizophrenia in Polish population

Schizophrenia has been associated with a large range of autoimmune diseases, with a history of any autoimmune disease being associated with a 45% increase in risk for the illness. The inflammatory system may trigger or modulate the course of schizophrenia through complex mechanisms influencing neurodevelopment, neuroplasticity and neurotransmission. In particular, increases or imbalance in cytokine before birth or during the early stages of life may affect neurodevelopment and produce vulnerability to the disease. A total of 27 polymorphisms of IL1N gene: rs1800587, rs17561; IL1B gene: rs1143634, rs1143643, rs16944, rs4848306, rs1143623, rs1143633, rs1143627; IL1RN gene: rs419598, rs315952, rs9005, rs4251961; IL6 gene: rs1800795, rs1800797; IL6R gene: rs4537545, rs4845617, rs2228145, IL10 gene: rs1800896, rs1800871, rs1800872, rs1800890, rs6676671; IL10RA gene: rs2229113, rs3135932; TGF1B gene: rs1800469, rs1800470; each selected on the basis of molecular evidence for functionality, were investigated in this study. Analysis was performed on a group of 621 patients with diagnosis of schizophrenia and 531 healthy controls in Polish population. An association of rs4848306 in IL1B gene, rs4251961 in IL1RN gene, rs2228145 and rs4537545 in IL6R with schizophrenia have been observed. rs6676671 in IL10 was associated with early age of onset. Strong linkage disequilibrium was observed between analyzed polymorphisms in each gene, except of IL10RA. We observed that haplotypes composed of rs4537545 and rs2228145 in IL6R gene were associated with schizophrenia. Analyses with family history of schizophrenia, other psychiatric disorders and alcohol abuse/dependence did not show any positive findings. Further studies on larger groups along with correlation with circulating protein levels are needed.